Introduction to locking device 

➤Washers
➤ Locking Plates
➤ Wire Locking
➤ Circlips

Washers

Washers are used to provide a bearing surface area for nuts, acts as spacers or shim, and to apply a tension between a nut and the surface of the material to prevent the nut vibrating loose.

Locking Plates 

Locking plates are thin metal plate's places over a nut or bolt installation to provide positive locking of the nut or bolt.

Wire Locking

Is the most Positive and satisfactory method of ensuring that threaded fasteners remain secure under all conditions.

Circlips

part of the retaining family. The main advantage of retaining rings is that they reduce weight and are a cost saving device, due to the simplicity of design and use.

1. Washer
 










Plain Washer

Lock Washers (2 types)

 










 Spring Washer









Shakeproof Washer  





Countersunk Washers
 

 Self Aligning Washer












Tab Washers




Pro-Load Indicating Washer (PLI)

 

2. Locking Plates

§Thin metal plate’s
§Places over nut/bolt installation to provide positive locking of the nut/bolt
§Quick to assemble and disassemble
§It will automatically locked by a smaller screw/bolt
§Then use lock wire/self locking nut to tight it up
§Used at aircraft wing

Cotter Pins (Split Pins).

• 2 types of cotter pins.

Cadmium Plated, Low Carbon Steel Split Pin	Corrosion Resistant Steel Split Pin
-          Used for safetying bolts, screws, nuts, other pins.	-          Used in location where non-magnetic material is required and where resistance corrosion is desired.

Safetying (Cotter Pins/Split Pins).
1. Prefferred Method.
One leg of split pin is bent up over the emd of the bolt and other leg bent down over one of the flats of the nut.

2. Optional Method.
The split pin is rotated 90 degrees and the legs wrapped around the castellations.


General rules apply to cotter pins safety.
1. Leg bent over the bolt end should not extend beyond the bolt diameter.
2. Leg bent down should not rest against the surface of the washer.
3. If the optional wrap around method is used, the legs should not extend outwards from the side of the nut.
4. All legs should be bent over a reasonable radius.


Flathead Pins (Clevis Pin).
- Used with tie-rod terminals and in secondary control.
- Usually installed head up so that if the cotter pin fail, it remains at the same place.

Roll Pins.
- In tubular shape and has a slot running its full length.
- Inserted with hand tools and is compressed as it is driven into place.

Taper pins.
- Used in joints which carry shear loads.
- Plain Taper Pin.
  ￫ drilled and safetied with locking wire (A).
- Threaded Taper Pin.
  ￫ used with taper pin washer and shear nut safetied with a split pin/ a self-locking nut (B).

Grooved Pins.
- A fastener that is pressed into an appropriate sized.
- provide the proper interference fit to lock the fastener in place.

*Pal Nuts.
- known as check nuts/ lock nuts.
- Usually attached on the main nut.
- To prevent nut from slackening off.

3. Wire Locking.

- A positive locking devices method.
- To ensure that threaded fasteners remain secure under all conditions.
- Method of wiring together any 2/more components.
(nuts, bolts & screws)

• Single Wire (SW)

- used on small screw in a closely spaced geometrical pattern, parts in electrical system & plates that are difficult to reach.

• Double Twisted (DT)

- the most common method of safety wiring.

- Safety Wire Specifications.

Quick Release Fastener

• To secure inspection plates,doors and other removable panaels on an aircraft
• Also refer as turnlock,quick-action and stress panel fastenersi,it is easy to remove
• Type of Fasteners
• Dzus
• Camloc
• Airloc

Dzus Fastener

-Act as a holding device for the stud

-Consist of

1. Stud
2. Grommet
3. Receptacle

Camloc Fasteners

-Have variety styles and design

-Common used are the 2600,2700,4001,4002 series(regular line),panel fastener(heavy-duty-line)

-Two types of receptacles:

1. Rigid
2. Floating

-Stud and grommet installed in the removable portion.The receptacle is riveted to the structure of the aircraft.

-Type of stud and grommet depends on the location and thickness of the material involved

-Clockwise turn will lock the fasteners,while counter-clockwise will unlocked it.

Airloc Fasteners

-Consists 3 parts

1. Stud(steel and case hardened to prevent excessive wear)
2. Cross pin
3. Stud Receptacle(fabricated from high carbon,heat-treated steel)

-3 head of styles:

1. Flush
2. Oval
3. Wing

-2 types of receptacles:rigid,floating

-Size are classified by number:No.2,No.5 and No.7

-Classified by centre to centre distance between rivet holes of the receptacles:

• No.2:3/4 inch
• No.5:1 inch
• No.7:1 3/8 inch

4. Circlips.

-A type of fasteners(part of retaining ring family)

-Consist of a semi-flexible metal ring with open ends which can snapped into place.

-Advantages:Reduce weight and are a cost saving device.

-Have intrnal and external applications.

-Most circlips sit in a recess,other types have a self-locking action.

-Installation and removal procedure need to use special circlips pliers(Have different internal and external plier,but also have both)

Videos for you to understand locking devices better